The present invention relates to a cartridge case specially for a smooth bore gun.
More specifically, and in accordance with document EP-A-0 308 352, the present invention relates to a cartridge case comprising three elements made of plastic, namely:
a tubular body, made of semi-rigid plastic, such as high-density polyethylene, with an assembly end which tapers into the shape of a cone frustum; PA1 a base, made of a very rigid plastic such as polyoxymethylene, which has a frustoconical bore with substantially the same vertex angle as the tapering assembly end of the tubular body, to which it is matched in order to act as a housing; PA1 a bottom piece, made of slightly flexible and elastic plastic such as a polyethylene or a polyamide, with a frustoconical external profile of substantially the same vertex angle as the tapering end of the tubular body and as the bore of the base; PA1 the respective dimensions of the bore of the base and of the frustoconical external profile of the bottom piece being such that when these components are assembled, the annular gap between them has a width smaller than the thickness of the tapering end of the tubular body; PA1 as well as means for snap-fastening the base and the bottom piece together. PA1 differentiating the required functions of mechanical integrity and of sealing in the frustoconical region of connection between the tapering assembly end and the frustoconical bore of the base, and for this, making a sealing region and an assembly region which are distinct and superimposed in the axial direction of the tubular body interact in this connection region; PA1 obtaining this assembly region in the form of a welded plastic joint, known per se, between the tapering end of the tubular body and the frustoconical bore of the base; this joint is obtained by placing, using appropriate tooling defining a gap of trapezoidal diametral cross-section, the wall of said tapering end of the tubular body and the lateral wall facing it of the base, between the two electrodes of a sonotrode; PA1 obtaining this sealing region by tightly fitting together on the one hand, a lip belonging to the base, and on the other hand, a ring belonging to the tapering assembly end of the tubular body, fitted into said lip, this sealing region being arranged above the region of welding, in the direction in which the base is arranged at the bottom of the cartridge case; this sealing means is therefore different from the wedging or crushing of the tapering end of the tubular body between the bore of the base and the external profile of the bottom piece, as described in document EP-A-0308352; PA1 the arrangement of the anterior boundary of the tubular body some distance from a posterior shoulder of the base, this also making it possible to limit the wall thickness of the base, which wall is arranged between the two electrodes of the sonotrode during welding, and thus making it possible to obtain a continuous and therefore sealing welded joint; PA1 and limiting the extension, along a generatrix of the frustoconical connecting region, of the region for assembly using plastic welding between, on the one hand, a frontal boundary or circumferential line distant from or identical to the anterior boundary of the tubular body, that is to say its assembly end, and, on the other hand, a distal boundary short of the posterior circumferential line of contact between said base and the tapering assembly end of the tubular body, this being in order to maintain most of the taper wedging effect between the tapering end and the frustoconical bore of the base in the sealing region. PA1 a region of sealed connection between a ring belonging to the tapering assembly end of the tubular body and a lip belonging to the base and into which said ring is fitted, said sealed connection region extending from the posterior line of contact between the base and said assembly end; PA1 a collar of welding between the assembly end and the frustoconical bore of the base, extending from a distal boundary adjacent to or some distance from the sealed connection region to a frontal boundary adjacent to or distant from the anterior boundary of the tubular body; PA1 this anterior boundary of the tubular body being arranged some distance from a posterior shoulder of the base.
The object of the present invention is to improve the mechanical integrity and sealing of the assembled cartridge, on the one hand, as regards the previously defined case, and on the other hand, as regards a priming device or primer mounted in the bottom piece. This is because in a multi-barrel or multiple shot gun, the combustion of the powder contained in a struck cartridge subjects any neighboring cartridge, which has not been struck, to a shock or even to repeated shocks adversely affecting or even reducing its mechanical strength, or even the overall sealing of the previously defined case.
The subject of the present invention is a cartridge case as previously defined, making it possible to improve and preserve the sealing of the combustion chamber defined by the inside of the tubular body, the recess that there is in the bottom piece, and the posterior face of the priming device or primer fitted into a housing provided for this purpose in the bottom piece. This is because this sealing is essential for improving the efficiency of the cartridge.